US3491590A

US3491590A - Power stopper weight transfer apparatus

Info

Publication number: US3491590A
Application number: US723772A
Authority: US
Inventors: Billy K Watkins
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-04-24
Filing date: 1968-04-24
Publication date: 1970-01-27
Anticipated expiration: 1987-01-27

Description

n- 1970 B. K. WATKINS POWER STOPPER WEIGHT TRANSFER APPARATUS Filed April 24. 1968 3 Sheets-Sheet 1 BY M ' POWER STOPPER WEIGHT- TRANSFERQFPARAI'US Filed April 2.4, .1968

BQKk WATKINS h 3 Nb n I g W W L 5 i; (I! x N N v mw N A nM NM V v I I ATTORNEYS Jan. 27, 1970 :5. K. WATKINS 13,491,590

' POWER STOPPER WEIGHT TRANSFERAPPARATUS Filed April 24 1968 3 Sheets-Sheet 5 INVENTOR.

BILLY K. WATKINS l I I I I z ATTQRAEYS United States Patent 3,491,590 POWER STOPPER WEIGHT TRANSFER APPARATUS Billy K. Watkins, Lovington, 11]. 61937 Filed Apr. 24, 1968, Ser. No. 723,772 Int. Cl. G01] 5/13 US. Cl. 73141 Claims ABSTRACT OF THE DISCLOSURE When pulled forwardly by an attached sled, the weight transfer apparatus of the invention gradually and responsively shifts its center of gravity from a rearward position generally over a relatively frictionless undercarriage to a forward position over the sled. The shift in center of gravity is produced by a weighted trolley which is moved from the rear to the front of the apparatus along an elongated main support in response to forward movement of the apparatus by a cable-pulley system wherein one end of the cable is attached to a fixed point not on the apparatus and the other end is attached to the apparatus. An automatic trolley release mechanism disengages the trolley in response to movement of the apparatus to assure consistent starting conditions. A trolley braking and return system assures constant tension in the cable-pulley system and facilitates re-positioning of the trolley on the apparatus.

BACKGROUND OF THE INVENTION This invention relates generally to a weight transfer apparatus in which the center of gravity may be moved along the length of the apparatus in response to movement of the apparatus itself. In particular, the invention is readily applicable to measure the pulling energy of vehicles and particularly tractors so that a comparison may be made between competing tractors. When used in tractor pulling contests, the apparatus is commonly referred to as a power stopper in that it acts to produce an increasingly greater resistance to the pull of the tractor until the tractor is substantially slowed or actually stopped.

DESCRIPTION OF THE PRIOR ART It has been common in tractor pulling contests to provide a large, fiat ground engaging sled to be towed behind the pulling tractor and to weight it with a constant dead weight and an increasing live weight in the form of human bodies. The increasing weight of human bodies was added during the pull by persons strategically placed along the course of the pull who would jump on the sled as it passed their predetermined position. In the course of a pull, a large number of persons would have been added to the sled. In addition to the possible injury of the participating persons, there were other disadvantages that made the reliability of such a method of relative measure poor. Thus, for example, the weight of the participating persons would all be different, the point in time during the course of the race when they jumped on the sled would not always be the same and the same persons were not always available for each contest. To replace this prior crude, inconsistent method, I have invented a simple, very accurate and reliable weight transfer apparatus or power stopper.

SUMMARY OF THE INVENTION In the environment of a tractor pulling contest, the apparatus of my invention is generally used in combination with a sled, the rear portion of which extends below the front portion of my apparatus for a short distance, and a sled bolster which is attached to the rear of the sled and the forward portion of my apparatus to support the apparatus and transfer its weight to the fiat, flexible ground engaging sled. conventionally, the sled may be large, flat piece of steel which slides over the ground and has a frictional resistance to its movement which varies in relation to the weight it supports. The rear portion of my weight transfer apparatus is supported by a means which allows relatively friction free movement of the apparatus over the ground. Such a means may be a wheeled-undercarriage.

Basically, the weight transfer apparatus comprises a main support having front and rear portions, a supporting framework and a transporting undercarriage for said main support, a weight receiving trolley movably mounted on said main support, and a means to move the trolley on the main support between the rear and front portions in response to movement of the apparatus.

In its initial position, the weighted trolley is generally positioned over the undercarriage in the rear portion so that the center of gravity of the entire apparatus is generally over the undercarriage. During the pull, the trolley is moved by a cable-pulley system along the length of the main support until at the final position, the weighted trolley is in the front portion of the apparatus extending over the sled bolster and sled so that the center of gravity of the apparatus is generally over the connection of the apparatus with the sled bolster. It may thus be seen that as the apparatus is moved forward an increasingly greater amount of its weight is transferred from the rear generally frictionless undercarriage to the forward ground engaging sled so that the resistance of the sled to pull is uniformly and greatly increased.

The trolley should be of substantially shorter length than the main support beam and should be structured to allow the rapid addition and subtraction of weights therefrom. It conveniently has a front and rear monorail type carriage whose wheels ride along the lower flanges of the generally I-beam configured main support producing a low slung apparatus. Movement of the trolley along the main support is accomplished by a cable-pulley system which includes a cable having a first end connected with a fixed point not on the apparatus and a second end adapted to be connected to the apparatus. This cable is threaded to one of a bank of pulleys at the very forward portion of the apparatus back through a bank of pulleys on the trolley so that the forward movement of the trolley is geared down from the forward movement of the apparatus. The particular relative rates of movement may be varied to suit particular conditions. In practice, the forward pulleys may be attached to frame members depending from the front front of the main support. The number and positioning of the pulleys also will depend upon the particular conditions.

In addition to the basic structure set out heretofore, I have included a braking and trolley return system which I positioned in the rear portion of the main support and which serves to keep a constant tension on the cablepulley system and to regulate the forward movement of the trolley. AlsO, the system allows the trolley to be quickly returned to its initial rearward position. This system comprises a pulley attached to the trolley, a rotating brake means, a reel connected with the brake means, a cable wound on the reel and over the pulley on the trolley, and a crank handle connected with the brake means so that the crank handle may be used to move the trolley from the front to the rear portion of the main support. While my apparatus includes a manual return means, it is of course understood that a suitable power assisted return means may be provided instead. To assure a constant braking force, I provide a brake force control means which comprises a pivotal brake arm that is mounted on the apparatus adjacent the front end, a

pulley on one end of the brake arm and a brake control rod attached to the other end of the arm. The cable is supported by the pulley on the arm so that the tension forces in the cable provide the real control when they are transmitted through the pivotally mounted brake arm, through the control rod and through several direction changing links to the rotating brake means.

Consistent starting and operating conditions of the measuring means in a tractor pulling contest are important to assure accuracy. To provide this consistency, I include on my weight transfer apparatus an automatic trolley release mechanism which functions automatically upon a movement of the apparatus to release the trolley mechanism. This mechanism is usually positioned at the rear portion of the apparatus and comprises a release yoke through which the cable passes, a means on the cable adapted to engage the yoke as the apparatus is moved, a spring biased jaw pintle means cooperating with the yoke, a release pin, the release pin engaging the spring biased jaw to hold it closed, a release bar on the trolley, said release bar being engaged by said closed jaw and a positive pintle release wedged between the yoke and the jaw to prevent accidental engagement of the release pin. The jaw member is biased openly with a spring means so that when the pin is removed in re sponse to movement of the yoke and connecting linkage, the jaw snaps open and releases the release bar of the trolley. At the same time, the positive pintle release falls into place to prevent the accidental engagement of the release pin.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 shows the weight transfer apparatus in combination with a sled carrying a dead weight tractor and a pulling tractor as the apparatus would appear near the end of the tractor pull when the weighted trolley has been pulled forward to a position overlying the sled.

FIGURE 2 shows the weight transfer apparatus as it would appear in its initial position with the trolley rearward before the pulling tractor has been attached and the pull begun.

FIGURE 3 is a top view of the weight transfer apparatus as it would appear in its initial position before the pulling begins.

FIGURE 4 is a side view of the apparatus of FIG- URE 3.

FIGURE 5 is an end view taken along the line VV in FIGURE 4.

FIGURE 6 is an enlarged view of the end of the weight transfer apparatus having the automatic release mechanism as seen along the line VIVI in FIGURE 3.

FIGURE 7 shows a further enlarged view of the automatic release mechanism with the pintle in an open position.

FIGURE 8 is a top view of the automatic release mechanism of FIGURE 7.

FIGURE 9 is a cross sectional view through the weight transfer apparatus showing the main beam and the Weight transfer trolley with the weights attached.

FIGURE 10 is a view taken along lines XX in FIG- URE 3 showing a part of the braking system.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIGURE 1 schematically illustrates an energy measuring means comprising a pulling tractor 10, a sled 20, a sled bolster 23 and a weight transfer apparatus 30. The pulling tractor 10 is attached by chain means 11 to a forward edge of the sled and the weight transfer apparatus is attached to the rear edge of the sled by means of the sled bolster 23. A tractor 21 is shown in position on the sled 20 to provide a constant dead weight. The sled 20 may be a large flat, somewhat flexible piece of metal or similar substance which is pulled across the ground and of course is in frictional engagement with 4 the ground. The weight transfer apparatus of my invention is shown attached to the opposite end of the sled where it exerts an increasingly greater weight on the sled as the measuring means is moved.

As shown in FIGURE 1 the weight trolley has just about reached its forward point so that substantially all of the weight of the weight transfer apparatus is now bearing on the sled and of course increasing its frictional resistance. This position of the weight transfer trolley 50 may be contrasted with the position of the weight transfer trolley 50 in FIGURE 2 where it may be seen that a substantial portion of the weight transfer trolley 50 is to the rear of the weight transfer apparatus wheels so that relatively very little weight is transferred through the weight transfer apparatus framework to the sled 20.

FIGURE 2 shows the weight transfer apparatus as it appears at the beginning of the pull and before the pulling tractor 10 has been attached. From a comparison of FIGURES 1 and 2 the progress of the weight transfer trolley 50 along the main support 31 of the weight transfer apparatus is evident. As the tractor 10 pulls the sled and the attached weight transfer apparatus 30 forward or to the right in FIGURES 1 and 2, the cable opcrates through a system of pulleys best seen in FIG- URES 3 and 4 to move the weight transfer trolley along the main beam 31 until at a specified point the weight transfer trolley 50 may move forward no further. This relative change in position of the weight transfer trolley with regard to the weight transfer apparatus produces a movement in the center of gravity from the rear to the front portion of the apparatus 50.

Referring to FIGURES 3 and 4 the structure of the weight transfer apparatus and the attached sled bolster may be seen. The weight transfer carriage frame 30 includes an elongated main beam 31 which preferably may be in the shape of an I-beam. In actual practice this beam may be 20 to 25 feet in length. A upporting framework for the main beam 31 is generally indicated at 32 and may be seen to comprise a vertical strut and several inclined struts on either side supporting an axle 33 below the main beam. In addition this supporting framework 32 includes suitable lateral framework for the carriage frame.

The axle 33 is of conventional structure and has wheels 34 at either end. In my preferred embodiment the spread of the wheels is approximately 6'. The location of the wheels with respect to the length of the beam is important. With a beam having a front to rear length of approximately 25' and a trolley of about 10', I have found it suitable for purposes of my invention to place the wheeled undercarriage approximately 7' from the rear end of the beam. This relative location in the rear portion of the beam is important as will hereinafter be set out, to insure the adequate variance in the distribution of weight along the beam.

A weight transfer trolley generally indicated at 50 rides along the main beam from one end of beam 31 to the other. I have found it desirable to make the trolley 50 of a trolley beam 51 suspended below the main beam 31 by mono-rail type trolley beam supports 52 which may be conveniently placed for purposes of weight distribution at the front and rear quarter points of the trolley beam. Rear trolley wheels 53 and front trolley wheels 54 in the support 52 are shown in FIGURE 9 riding on the bottom flange of the main I-beam 31. This trolley wheel carriage includes the necessary axles for the wheels and a pair of vertical wheel support members 55 depending from the outside of either wheel which are held in fixed relationship with respect to each other and with respect to the trolley beam supports 52 by tie rod spacer means 58. For the trolley beam itself, we have found that an H- shaped beam 51 as best seen in FIGURE 9 is suitable because it provides a convenient means upon which to mount C-shaped weights 59. In practice these weights each weigh about pounds and extend along both sides of the approximately trolley beam 51 so that the trolley will be very weighted. The exact Weight may be easily varied. A heavy trolley weight relative to the remainder of the apparatus assures that the center of gravity of the apparatus will be shifted from a rear position approximately above the axle to a forward point on the apparatus approximately at the point of attachment with the sled bolster 23.

The sled bolster 23 has for its purpose the transfer of weight from the weight transfer apparatus to the sled 20. A construction of the sled bolster suitable for the typical flat sled includes a pair of horizontal bottom members 24 placed one on either side of the main beam, a transverse member 26 connecting the pair of bottom members, a pair of vertical frame members 27 projecting upwardly from the intersection of the bottom member 24 and the cross member 26 and a brace member 28 rigidly fixing the members 24 and 27 with respect to each other. To provide for the connection to various width sleds a laterally extensible connector 25 is provided which may slide in an opening in the cross member 26.

As may be seen from FIGURES l and 2 the sled ordinarily will have a cylindrical pipe attached at either end to provide a means of connection between the pulling tractor and the weight transfer apparatus. The connection of the sled bolster 23 to the weight transfer supporting frame 32 is effected by a bolster pin 29 passing through a suitable connecting structure of the carriage frame and into the structure of the sled bloster 23 which will allow relative pivotal movement between the sled bolster and the weight transfer apparatus. It is to be understood that the structure of the sled bolster and its connection with the weight transfer apparatus may be varied in accordance with the various constructions of the sled 20.

The main beam 31 may be provided at its extreme front and rear ends with frame members which serve to support the necessary Weight transfer apparatus struc ture. Thus, a front vertcial frame member 38 may support a front shock absorber spring 37 and certain of the pulleys for the pulley system. Likewise, a rear vertical frame member 35 may depend from the main beam to support a rear shock absorber spring 36 and various trolley operating mechanisms. Positioned on either end of the weight transfer trolley 50 are rear and front trolley bumpers 56, 57 respectively which are aligned with the rear and front shock absorber springs 36, 37 respectively to safely limit the travel of the weight transfer trolley 50 along the main beam 31.

Movement of the weight transfer trolley 50 along the main beam from a position at the rear end of the weight transfer apparatus to a position at front of the apparatus is provided by a pulley system wherein a cable 70 is attached at one end 79 to a fixed point not on the weight transfer apparatus and on the other end 78 to a point on the weight transfer apparatus. Intermediate of these two points the cable 70 passes through a series of pulleys which reduce the relative travel of the trolley on the weight transfer apparatus in relation to the distance traversed by the weight transfer apparatus so that ordinarily movement of the trolley will be at a much slower rate than the movement of the weight transfer apparatus.

As may be best seen in FIGURE 3 the end 79' of the cable 70 may have a ball stop thereon which engages an eyelet stake 72 usually driven in the ground. Movement of the weight transfer apparatus once the stop has engaged the stake will result in movement of the trolley through the pulley system. The pulley system generally comprises a brake arm pulley 62, a bank of pulleys 60 attached to a forward portion of the weight transfer trolley, and a bank of pulleys 61 attached to the front vertical frame member 38. The cable 70 has been designated in terms of portions. Thus, cable 74 represents that portion of the cable between the ball stop 70 and a quick release cable eye 73, while portion 75 represents the cable between cable eye 73 and brake arm pulley 62. Cable portion 76 extends between the brake arm pulley 62 and the pulleys 60 and cable portion 77 represents the numerous strands between the bank of pulleys 60 and the bank of pulleys 61.

In operation as the weight transfer apparatus moves forward the cable portion 75 will increase in length and the

cable portions

76 and 77 will have a total decrease in length equal to the increase in the length of portion 75; however, this total decrease in the length of

portions

76 and 77 must be divided by the total number of cable strands in the

portions

76 and 77 to arrive at the net forward movement of the weight transfer trolley member. It may be seen that the relative rate of movement of weight transfer trolley will depend on the number of strands in the

cable portions

76 and 77 between the pulley members 60 and 61. These will vary depending on the relative desired movement of the trolley member.

To keep the cables and pulley system under tension the weight transfer trolley has been provided with a braking system as may be best seen in FIGURES 3, 4, 5, 6 and 10. With the weight transfer trolley 51 moving from rear to front during the normal operation of the weight transfer apparatus, the braking means is preferably positioned at the rear of the weight transfer apparatus and I have found it convenient to mount it on the rear vertical frame member 35.

The braking means has several purposes the first of which is to keep a constant tension on the pulley system and thereby assure that the travel of the weight transfer trolley is smooth and uniform. A second purpose of the brake is to provide a means of pulling the weight transfer trolley back to the starting rearward position after a pull. To accomplish these purposes the brake means comprises a brake drum 107 having a brake band 108 almost entirely around its circumference except perhaps for an area of say 20 degrees. The brake drum and brake band material are conventional and the sizes of both will of course vary with the relative size of the weight transfer apparatus. Each end of the band is upturned in substantially right angular relation and has extending therethrough a pin and spring means. One end of the pin engages one of the upturned ends and the other end of the pin engages a brake band camming arm 101 such that when an arm 102 is pivoted counterclockwise it compresses the band 108 about the drum 107 to exert a braking force.

Movement of the weight transfer trolley is transmitted to the brake drum by a pulley arrangement which has a cable 112 anchored at one end to the rear vertical frame member and extending half way around pulley 113 on the trolley to be wound on a brake cable reel 111 located on the apparatus frame. The brake cable reel 111 is connected to the brake drum 107 either directly or through a system of gears so that any movement of the trolley is directly transferred to the brake drum 107. A crank handle 110 is mounted on the brake drum and serves as the means by 'which the trolley is returned to its rearward starting posi tion after a typical run.

Since the braking system has a direct influence on the force necessary to pull the weight transfer. apparatus and the trolley forward it is important that the pressure or force exerted on the brake drum be equally determined for each contestant. I have found that the fairest way of operating the braking system is to have itfunction in proportion to the forward force exerted by the tractor pull contestant. To provide for this uniform braking condition I have mounted the pulley 62 on one end of a brake pulley arm which is pivotally connected at 92 to the forward end of the main beam 31 and which has a brake control rod 94 attached to its other end to transmit the force of the cable and the pulley system rearwardly to the brake system on the rear of the weight transfer apparatus. A guide 91 positioned at a point along the length of the brake pulley arm 90 serves to guide its movement and a control rod return spring 93 attached to the same end as the brake control rod 94 provides a tensioning means to prevent loose play in the system.

The force of the pulley system as transmitted through the brake control rod 94 is transferred by a pivotal direction changing plate 95 as best seen in FIGURE 6 through a control rod portion 96 into an adjustable lever arm 97. From the lever arm 97 this force is transmitted by the torsion pin 99 through a brake lever portion member 100 and a brake band camming tension arm 101 to the brake band camming arm 102. As set out heretofore the arm 102 compresses the band 108 about the drum 107 so that the pulley arrangement 112 brakes the movement of the weight transfer trolley 50. To allow external control of the braking system a trolley brake hand lever 98 is provided. Adjustment of the braking force to changing conditions is made possible by a brake tension spring 103 which is attached at its lower end to the brake band camming arm 102 and at its upper end to a brake tension spring adjustment rod 104 which, being adjustably mounted on frame support 105, may be adjusted to vary the tension on the spring 103 that actuates camming arm 102.

It is to be understood that in a contest where the differences between the various contestants may be very small it is extremely important that each contestant compete under substantially the exact same conditions as the other. An area of particular importance in a tractor pulling contest is the very beginning. To assure that the contestants each have an equal start, I have devised two mechanisms; both, or either of which may be included on my weight transfer apparatus. First I have provided an eyelet stake 72 through which the cable portion 74 extends and against which eyelet the ball stop 70 at the end of the cable will be caught as the pull begins. The second mechanism, an automatic trolley release mechanism, is somewhat more complex and has for its purpose the anchoring of the weight transfer trolley during movement of the weight transfer apparatus other than those times in which it is being pulled in a contest. A further purpose is to assure that movement of the trolley begins at exactly the same moment for each contestant.

The automatic trolley release mechanism may be best seen in FIGURES 3, 5, and 8. Thus, in FIGURE 3 it may be seen how the quick release cable eyelet 73 is situated with respect to the automatic release mechanism yoke 130. Cable portion 74 passes through the upstanding fingers of yoke 130 until the cable eyelet 73 is encountered at which time the forward progress of the weight transfer apparatus will cause the eyelet 73 to pivot the yoke 130 rearwardly about a pivotal mounting 131. FIGURE 8 shows the yoke mounted outwardly of the rear portion of the weight transfer apparatus on a frame support member 132. When the yoke 130 pivots, it moves, in turn, an adjustable tie rod 133 and pivots a rigid release arm 134 to disengage a release pin 135 so that a spring biased pivotal upper pintle jaw 137 is opened and a trolley release bar 138 mounted on the transfer trolley 50 is disengaged to allow movement of the trolley. Arm 134 is conveniently mounted on a support 140. I have made the release pintle with a fixed lower pintle jaw 136 that cooperates with the pivotal upper pintle jaw to securely grasp the trolley release bar 138. A spring 141 biases the upper jaw 137 open. When the upper jaw 137 snaps upwardly upon release of the pin 135 a spring loaded door 142 snaps into position between the jaw members to prevent any possible accidental reclosing of the pintle jaws.

As an additional safety means to prevent the pin 135 from accidentally being pushed back into engagement, I have provided a safety mechanism having a positive pintle release support 144 mounted on the arm 134. A positive pintle release arm 143 is pivotally attached at one end 'to the support 144 and has at its other end a notch cut out along its bottom to allow the arm to slip over at least a portion of the pintle support 146. It may thus be seen that when the arm 134 moves to release the spring loaded pintle 137 the positive pintle release arm 143 moves outwardly and the cut-out 145 allows it to drop by gravity over the top of the pintle support 146 so that the arm 143 will now prevent the arm 134 from moving inwardly again towards the pintle support 146. Thus, the pin cannot move inwardly and accidental locking of the pintle is prevented.

To move the weight transfer apparatus about from place to place and to return the apparatus to a starting position af-.er the end of a contest, I provide a pivotal hitch bar 40 attached at one end, as may be best seen in FIGURE 5, to the axle 33 and having at its other end a hitch 41 and a hitch ring 42. To allow adjustment of the hitch to various sized tractors, a height adjustment and transport bar 43 is provided. This bar is attached at its lower end to the hitch and at its upper end passed through an adjustment collar 45 which adjustment collar is pivotally attached to the apparatus frame at 46. The adjustment and transport bar has holes 43 along its length and by suitable means is securely adjusted to the particular desired height.

To secure the weight transfer trolley during the movement of the apparatus from contest area to contest area, a suitable securing bolt 117 keeps the trolley firmly against the rear shock absorber spring 36. As shown, the bolt 117 has a curved end passing through a bolt plate 118 on the trolley and its other end passing through a bolt plate.

119 on the rear vertical frame member 35. Use of the bolt 117 prevents wear and tear of the automatic release mechanism when the apparatus is moved over long distances.

OPERATION OF THE WEIGHT TRANSFER AP- PARATUS DURING A TYPICAL CONTEST IS AS FOLLOWS:

In its initial position, the weight transfer apparatus has a cable anchored at one end to a stake 72 and is attached by means of a sled bolster 23 to a sled 20. Initially, the weight transfer trolley 50 is in its rearward position on the main support 31 and the automatic release mechanism is firmly grasping the trolley release bar 138 so that forward movement of the trolley is prevented. As shown in FIGURE 2, the sled bolster 23 positions the main beam at a slight incline, however, this is not necessary and may be adjusted to suit the particular contest conditions. In its initial position, again referring to FIGURE 2, the weight transfer apparatus has its center of gravity substantially over the wheeled undercarriage and is well balanced sothat little weight is transferred to the sled 20 by the sled bolster 23. At that point in the contest, the pulling tractor 10 is mainly pulling against the ground friction of the sled due to the dead weight represented by the tractor 21. After the initial instant of forward pull, however, the cable eye 73 engages the yoke as previously set out and the automatic release mechanism is automatically disengaged from the trolley 50. As the pulling tractor continues to pull the apparatus forward, the pulley system moves the trolley 50 forward along the main beam 31 in a smooth and uniform manner. At the same time, the braking system exerts a braking force at the rear of the trolley to keep the pulley system under constant tension. This braking system as Was heretofore set out applies a braking force directly related to the pulling force as evidenced by the tension in the pulley system so that an even and uniform balance is maintained in the apparatus. It may be seen that as the trolley moves uniformly forward, the weight transferred to the sled 20 through the sled bolster 23 increases because of the shifting center of gravity of the weight transfer apparatus until at the very forward point of the weight transfer trolley generally shown in FIGURE 1 the center of gravity of the apparatus has shifted to a point over the sled and the 9 frictional resistance of the sled has been correspondingly increased.

If the tractor pulling contest is from a standing start over a fixed pull distance, the time in which the distance was negotiated will provide the distinguishing characteristic. Likewise, if there is a flying start, which it will be noted is possible with my invention because of the use of the eyelet stake with the ball stop at the end of the cable, time again will be the measuring criterion. If the time is set, then the distance which the tractor has travelled in the set time may be easily and quickly measured. Regardless of the particular type of contest, however, it may be seen that my apparatus providesan exact, uniform and easily adjustable means of measurlng the output of the various contestants. The weight or the braking force desired may be rapidly and quickly varied. Variance of the weight is easily accomplished by merely adding or subtracting from the weights 59 which are applied to the trolley beam 51, while the increase or decrease of the braking force is readily accomplished through the use of the adjustment means 104 for the brake tension spring 103.

At the end of a pull, the apparatus may be very quickly and rapidly returned to its starting position by attaching a suitable pulling means to the hitch 42 and pulling the apparatus back to its rearward position. Through the use of the crank handle 110 attached to the brake drum 107 which works through the pulley system 112 and 113, the trolley member may be easily pulled back to its rearward starting position. At this point, the automatic release mechanism is re-engaged with the trolley member and the apparatus is ready for the next contestant.

From the foregoing description it may be seen that I have invented an apparatus well suited to the requirements of measuring forces and particularly well suited to measure the forces expended in tractor pulling contests. I have merely set out the principles by which my invention operates and explained one means of carrying out my invention operates and explained one means of carrying out my invention under the disclosed principles. It is within the contemplation of this invention, however, to provide other equivalent means to carry out my invention.

Although minor modifications might be suggested by those versed in the at, it should be understood that I wish to embody within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of my contribution to the art.

II claim as my invention:

1. A device for indicating the relative pulling force exerted by a power source comprising a sled adapted to be connected to and moved by said power source, and a weight transfer apparatus having a front portion supported by said sled and a rear portion supported by means which allow relatively friction free movement of said apparatus, a relatively movable mass, and means to move said mass in the direction of said front portion a distance proportional to the distance through which the device is pulled, whereby the distance through which the device has been moved provides an indication of the relative force exerted 'by said power source.

2. An apparatus for measuring and comparing energy expended comprising an elongated forwardly movable structure having a forward end and a rearward end, said forward end having an area of high frictional resistance to movement and said rearward end having an area of low frictional resistance to movement, a relatively large mass movable on said structure from an initial position adjacent said low friction area to a final position adjacent said high friction area, and means to move said mass in the direction of said forward end a distance proportional to the distance through which the structure is moved, whereby the distance through which the structure is moved provides an indication of the energy expended.

3. An apparatus according to claim 2 wherein the means for moving the mass proportionally to the movement of said structure is a block and tackle arrangement including a cable having first and second ends and at least two pulleys, said first cable end adapted to be connected with a cable take-out means and said second cable end adapted to be connected with said movable apparatus, at least one of said pulleys being attached to said apparatus and at least one other of said pulleys being attached to said movable mass, said cable being wound over said pulleys, said cable cooperating with said pulleys and said movable mass to move said mass between the rear and front portions of said structure in response to movement of the apparatus.

4. An apparatus according to claim 3 wherein said cable take-up means includes a fixed anchor means not on said mo able apparatus.

5. An apparatus according to claim 2 wherein the forward movement of said mass from said initial position to said final position is geared down from the forward movement of the apparatus so that the forward movement of the mass will be less than the forward movement of the apparatus.

6. An apparatus according to claim 2 wherein the weight of said mass may be incrementally varied.

7. An apparatus according to claim 2 including means for returning the movable mass from its final position to its initial rearward position including a reel, a cable having a first end wound about said reel and a second end attached to said movable mass, and power means for drawing said cable onto said reel.

8. A weight transfer apparatus according to claim 2 including a braking and trolley return system positioned in the rear portion of said main support, said system having a pulley attached to said trolley, a rotating brake means, a reel connected with said brake means, a cable wound on said reel and over said pulley on said trolley, a brake force control means and a crank handle on said rotating brake means to move said trolley from the front to the rear portion of said main support.

9. A weight transfer apparatus according to claim 8 wherein said brake force control means comprises a pivotal brake arm mounted on said apparatus adjacent said front end, a pulley on one end of said brake arm and a brake control rod attached to said other end, said cable being supported by said pulley so that tension forces in the cable are transmitted by said brake arm through said control rod, said brake control rod extending to said brake means to control the braking force.

10. A weight transfer apparatus according to claim 3 including an automatic trolley release mechanism having a release yoke, a means on said cable adapted to engage said yoke as said apparatus is moved, a spring biased jaw cooperating with said yoke, a release pin, said release pin engaging said spring biased jaw to hold it closed, a release bar on said trolley, said release bar being engaged by said closed jaw, said jaw being biased openly when said pin is removed, said release bar being disengaged by said open jaw, a positive pintle release mounted between said yoke and said jaw and adapted to prevent accidental engagement of said release pin.

References Cited UNITED STATES PATENTS 1,603,521 10/1926 Davidson 73141 2,768,823 10/1956 Lindars 177-214 RICHARD C. QUEISSER, Primary Examiner I. WHALEN, Assistant Examiner